X-ray imaging remains an important contemporary discipline in medical technology. Use of X-ray processes are in common practice in systems which range from real time images, usually of low resolution gastro-intestinal sections, taken by image intensifier-vidicon chains, to single shot images, examples of which are chest and mammography studies, normally captured and processed on film.
Although film based systems form the backbone of diagnostic radiology today, presently there is significant motivation to find and employ improved methods. That motivation comprises elimination of expensive and space-consuming photography development laboratories, of large film storage facilities, of levels of x-ray dosage required by film, of cost of silver halide film, of limited resolution in preferably low dose applications such as mammography, of finite and somewhat fixed sensitivity of film processes and of time and associated manpower required to process film itself and deleterious effect of film processing upon the environment.
Even so, at this time, the majority of chest and mammographic x-ray images are produced by film-based systems. A number of systems which produce images without film are currently being sold by FUJI Corporation of Japan, by Kodak and General Electric Corporations of the United States and by Siemans and Phillips Corporations of Germany. Generally, the majority of the above listed companies sell systems based upon FUJI technology which employs photo-stimulable luminescent methodologies. Somewhat differently, the Phillips system employs a selenium surface located on a rotating drum. Generally, these systems are used for chest x-ray imaging and other large body-area studies and have inherent resolution limitations. A first attempt to replace filmless mammographic x-ray processes, by Xerox Corporation, was abandoned due to high dosage requirements. Succeeding refinements reduced x-ray dosage but did not compete well against a rising tide of screen film mammography. This attempt was based upon an electrostatic latent image impressed upon a selenium plate and developed in a manner similar to early production of Xerox photocopying.
While each of the currently marketed filmless systems promises to fulfill an existing market niche, for replacing film based systems, there remains existing radiology requirements for imaging systems which have not been heretofore fulfilled. These requirements include an increase in resolution and a reduction in x-ray dosage for all applications, but foremost for mammography, rapid visual image production, low cost (especially for upgrading present film based systems) and wide dynamic range to void need for image retakes caused by over or under exposure are paramount for providing a commercially viable system. This instant invention provides innovative solutions to the above recited needs while providing a ready answer to other newly recited, but currently unreachable, objectives comprising filmless image subtraction to draw low contrast images out from high density image shadows and placing x-ray capability in heretofore unreachable environments, such as in emergency vehicles and the weightless environment of space.